Background. There is still a relative paucity of information about the long-term course of depression.

Methods. Consecutive patients admitted to a teaching hospital psychiatry unit with symptoms of depression, previously assessed at 6 months and 2, 5 and 15 years after index admission, were reviewed at 25 years (N = 49, including eight informants of deceased probands, of an original 145 with major depression (DEPs)). Prospective psychiatric (N = 22) and retrospective surgical (N = 50) control groups assessed after 25 years were used for comparison.

Results. A further decade of follow-up confirmed the chronicity of depression. Of depressed patients (DEPs) followed for the full 25-year-period only 12% of the 49 original DEPs recovered and remained continuously well, 84% experienced recurrences, 2% experienced an unremitting course and another 2% died by suicide. Note that in the first 15-year-period 6% (9/145 DEPs) committed suicide, a further 38 died and 32 were lost to follow-up. They experienced an average of three episodes of depression over the 25 years. In the decade since the 15-year follow-up, 27% improved in clinical outcome (including four of five previously chronically depressed patients), 55% remained unchanged and 18% worsened; and the number of episodes per year declined. Patients initially diagnosed with neurotic or endogenous depression had similar long-term outcomes. The criteria for a current DSM-III-R disorder were met by 37% of DEPs, including 11% with depression or dysthymia. On the global assessment of functioning scale 78% of the DEPs had some impairment compared to 62% of psychiatric controls and 40% of surgical controls.

Conclusion. Even after 25 years, severe depressive disorders appear to have poor long-term outcomes. Patients with chronic outcomes over 15 years can improve when followed over longer periods.